Method of and composition for reducing the octane requirement of an engine



United States Patent O ce M25357 r Patented Dec. 6, 1955 in ASTMBulletin, No. 154, October 1948, page 53 Betz725857 ter lead scavengingneeded for aviation gasoline, by E.

METHOD OF AND COMPOSITION FOR REDUCING THE OCTANE REQUIREMENT OF ANENGINE Cleveland, Ohio, a corporation of Ohio N Drawing. ApplicationMarch 19, 1954, Serial No. 417,516

Claims. (Cl. 123-1) The present invention relates to a method of andcomposition for reducing the tendency of an internal combustion engineto knock.

It is ell known that deposits quickly accumulate in the combustionchambers of internal combustion engines such as those used inautomobiles. An engine containing deposits is said to have a higheroctane requirement than a clean engine because it requires a gasolinewith a higher octane rating if the engine is not to knock. This becomesapparent to the driver of an automobile having a dirty engine by thetendency of the engine to knock while accelerating, climbing a hill orotherwise operating the engine under greater than normal load. Thedeleterious effects of such accumulations of deposits are particularlynoticeable in engines having a high compression ratio because the marginbetween the octane numbers of gasolines on the market and the octanerequirement of the engine when clean is narrower than for engines havinglower compression ratios. When such an engine becomes dirty the octanenumber of the gasoline required by the engine in order not to knock isincreased and often reaches a value higher than the octane rating ofgasolines generally available.

When the fuel used in an internal combustion engine contains tetraethyllead, an agent which in effect raises the octane rating of the fuel, theincrease in octane requirement of the engine with continued use becomesgreater than when non-leaded fuels are used, especially under mildconditions simulating ordinary driving. Thu-s, whereas the octanerequirement of an internal combustion engine operating on non-leadedfuel under the conditions of. a standard engine test describedhereinafter may increase from say 70 for a clean engine to 78 for adirty engine and then level oil? at that figure, the octane requirementin the same engine, if run on leaded fuel, will increase to 82 or morefor a dirty engine before levelling oit.

It has been found that the deposits in the combustion chambers ininternal combustion engines run on leaded fuel are different ondifferent surfaces, apparently because of their diiferent averagetemperatures. In an aviation engine, for example, the metal temperaturesof the piston, cylinder intake valve and exhaust valve are 300 to 500,400 to 600, 600 to 800 and 1000 to 1200 F., respectively. Thecomposition of the deposits appears to depend on the metal temperatureof the particular surface. Where the metal temperature is of the orderof about 400 F. the deposits analyze about 50 to 60% lead and consist offrom about 25 to 30% lead sulfite and lead sulfate, 20% lead monoxide,35 to 40% lead bromide and about carbon. Where the metal temperature isconsiderably higher, i. e., of the order of 1000 to 1200" E, the leadcontent is about 70% and the deposits are composed almost entirely oflead sulfate, lead sulfite and lead monoxide, the concentration of leadbromide being extremely small and the amount of carbon being practicallyzero. These observations are recorded A. Droegemueller. 7

It is well known, of course, that ordinarily the octane requirement ofan engine, whether it be an automobile, marine or airplane engine, isreduced in order to restore or at least to approach its originalefficiency by the process of removing a cylinder head and grinding orabrading off the deposits found on the various surfaces of thecombustion chamber, such as the piston top, the cylinder wall, cylinderhead and the intake and exhaust valves.

This method, while quite elfective, has the disadvantage of requiringskilled labor and a considerable amount of time to dismantle, clean andreassemble the engine. It is therefore responsible, when carried out onengines of commercial vehicles, for making it necessary to withdraw thevehicle completely from service while the engine is being overhauled. gY

A great number of other methods have been proposed heretofore forcleaning the combustion chambers of an engine without removing thecylinder head. One of these methods is that of introducing a liquidsolvent into the carburetor while the'engine is running. Although thismethod produces great billows of smoke at the exhaust,

it has been found, upon taking apart an engine so treated, that littleof the deposits are actually removed.

In accordance with this invention, the octane requirement of a dirtyinternal combustion engine, which term is intended to include sparkignition and fuel injection type engines, is reduced by coating thedeposit-bearing surfaces of the combustion'charnbers of a dirty enginewith a composition containing silverborate, copper borate or acombination thereof and then running the engine. The coating of thecombustion chamber wall surfaces may be accomplished in any desirablemanner, such'as by spraying or squirting the composition into thecombustion chamber through an opening such as that provided by removalof the spark plug or injection nozzle. The composition to be applied tothe dirty combustion chamber walls essentially comprises two components.One component is chemically .reactive with lead or its compounds underthe conditions within the combustion chambers of a running internalcombustion engine and comprises silver borate, copper borate or acombination thereof. The other essential component performs the purelyphysical function of adhering the reactive component to the combustionchamber walls and is a thick, tacky, metal-adhering material or mixtureof materials that is fairly viscous or non-flowable at ambienttemperatures, non-corrosive to the engine parts, and preferably readilyremovable from the combustion chamber by eventual volatilization and/orcombustion under the conditions in the combustion chamber.

In addition to the desirable reduction in octane requirement effected bythe composition and method of the invention, there is obtained, mostsurprisingly, a suppression of octane requirement increase in engineoperations following the application of the composition to thecombustion chamber surfaces. This additional effect is most advantageousbecause the coating operation not only reduces the octane requirement,but at the same time prolongs the effect thereof.

The copperborate may readily be prepared by reaction of borax withcopper sulfate or copper nitrate. The silver borate may be prepared insimilar fashion, e. g., by reaction of borax with silver nitrate.

Because of the purely physical function of the vehicle or carriercomponent, its chemical composition and structure are not particularlycritical so long as it is capable of carrying the borate, adhering tometal and combustion chamber deposits, and does not damage the engine.Generally, viscous and tacky hydrocarbons that are capable of beingvolatilized. or consumed under the conditions of combustion in thecombustion chamber of a running engine and thereby removed,, arepreferred as vehicles in the composition. Such vehicles or carriersinclude petroleum bright stocks,polybutenes,.petrolatums, hydro.- carbonoils thickenedrif v desired-,,to; gel fornrwith suitable thickeningagents such as hydrogenated castor oil, andgreases, particularly thesofter greases. One group of vehicles that has been found particularlyuseful comprises various mixtures of petroleum bright stock andv viscoussynthetic polybutene, in which the bright stock has a viscosity of about700 to 23.00 S. S. U. at-100I" F. and the polybutene has a molecularweight of about 700-to 1250.

Itv is, of. course, desirable that; the composition contains the highestpossible concentration, of. borate consistent. with. the requirements;that the composition, be fairly viscous and capable of adhering to thecombustionchanlber walls; andv particularly tothe: deposits: on thewalls. Withthese considerations in view,,the compositionofthe inventionshould contain at:least about by weight of borateto be elfective, and atleast suthcient vehicle, i. e., a minimum of about 10% by weight, toeffect the physical function of adhering the composition to thecombustion chamber walls.

The amount of borate introduced into each combustion chamber depends, aswill readily be understood, upon the weight and type of, deposits in thecombustion chamber, the dimensions of the combustion chamber, and theextent to which they are to be removed or rendered inactive in exertingan unfavorable catalytic effect on the combustion of the fuel in theengine. The amount of borate introduced into each combustion chamber inaccordance with this embodiment of the invention should therefore be an.appreciable. amount, i. e., sufiicient to effect the desired reduction:in octane requirement. For engines which have reached an equilibriumoctane requirement, i-. e., a requirement that will not increasesubstantially with continued; operation,.it has been found that amountsas low as aboutone gram of the borate per combustion chamber areeffective, amounts in the range of between about 5 and grams percombustion chamber being preferred. Amounts above about 25 grams percombustion chamber maybe utilized. so longas they are. insufiicient tointerfere with the operation of the engine, but are undesirable sincethey merely add to the expense but not to the effectiveness of thetreatment. Generally, therefore, it is desirableto introduce betweenabout 1 and 25,, preferably between about 5 and- 15 grams of the borateinto each combustion chamber. The amount of the, composition employedin, each, combustion chamber is governed by. the foregoingamounts aswell as by-the general considerations that a. coatingthereof should nothave a thickness exceeding about /s".

While it is to be understood thatthe scope'of, the invention is not tobe limited by any theory advanced herein,

it is believed that the lead in, the lead sulfate, lead sulfite and leadoxides forming the combustion chamber deposits in engines running onleaded motor fuels is, by reason of its variable valence, inanactive'state and: probably exerts an unfavorable catalytic effect onthe cornbustion of the fuel in the engine. It is believed that bytreating these lead salts with silver or copper borate, a.

binary compound is formed in the, deposits which the lead iscomparatively inactive, since it can no longer,

move freely from one valence state to another, and, itscatalytic actionis thereby inhibited.

The advantages and utility of the. invention: willbecome more apparent.from. the following example included herein for illustrative purposesonly:

Example Copper borate was prepared by; adding 1 cc. concentrated nitricacid to 30grams (0.125 mol') copper nitrate, Cu(NO3)z.3H'2O, in a fewcc. of water and adding the resultingsolution to a solution of 48 grams'(0.125 mol) borax, Na2B4O'1.1OH2O, in 250 cc. water heated to 140 F.washed several times with water and once with methanol, and then driedby spreading. Analysis of the precipitate showed it to contain 8.0%boron.

60 grams of the copper borate thus obtained were ground for four hoursin a mechanical grinder and mixed to a fairly smooth paste, referred toin this example as Paste A, with. 30 grams of Pennsylvania bright stockhaving a viscosity of1590 S. S. U. at F. and 30 grams of a viscous,synthetic polybutene, available commercially as oronite. polybutene No.24, having a molecular weight of about 840.

Silver borate was prepared by adding a solution, heated to F., of 435grams (1.5 mole) sodium tetraborate, NazBsOmSHzO (USP refined powder.)dissolved in 2100 grams of water, to a solution, likewise heated to 140'R, of 510 grams (3 mols) silver nitrate, AgNOs, dissolved'in 430grams-ofwater. A white precipitateformed immediately, was filtered,washed six times with water and twice with methanol, and spread out todry. It was further dried by use of an infra-red lamp. The solidprecipitate was found, upon analysis, to contain 7.3% boron.

50 grams of the silver borate thus obtained were ground for four hours.in a mechanical grinder and mixed to a smooth paste, referred to in thisexample as. Paste B, with 55 grams of the same Pennsylvania bright stockand 25 grams oronite polybutene No. 24."

A standard, clean, six-cylinder Chevrolet automobile engine was run ongasoline containing 3 cc. per gallon tetraethyl, lead under a standardprocedure designed to approximate ordinary driving conditions and dirtythe engine. This procedure, involves running the engine for five minutesat 2000 R. P. M., corresponding to a road speed of 40 M. P. H. withstandard. spark advance, an oil temperature of 190 F, and a watertemperature at the jacket outlet of F., and then running the engine forone minute at 500 R. P. M. under idling conditions. This six minutecycle was repeated until the octane requirement of the engine hadarrived at an equilibrium value. In measuring the octane requirement atintervals of, about eight hours,v the engine was operated under thefollowing conditions:

Spark advance l1- BTDC Air fuel ratio 13.5

After the octane requirement had risen from an initial. value of' 71 toan equilibrium value of 81, the spark plugs were removed andComposition. A, consisting of a mixture of 60 grams copper borate, 30grams of petroleum bright stock, and 30 grams of polybutene No. 24, wascoated on the combustion chamber walls of the dirty engine to athickness of about ,4,".

After the spark plugs were replaced, the engine testing procedurepreviously described was resumed and the octane requirement of theengine was measured after 1 and 26 hours of operation alternately at2000 and 500 R. P. M; It was found that the octane requirement of theengine was 82 after the first hour, and 74 after 26 hours.

The entire procedure was repeated with Composition 1?- consisting of amixture of 50 grams silver borate, 55 grams petroleum bright stock and25 grams polybutene No. 24. It was found that two hours after coatingthe combustion chamber walls of the dirty engine to the thickness ofabout Lg" with Composition B, the octane requirement had been loweredfrom the equilibrium requirement of 81 to a value of 77.

These tests show that both compositions etfected significant reductionsin octane requirements, thus indicat A blue precipitate formedimmediately, was filtered ing effectiveness in inhibiting undesirablecatalytic action on the part of the engine deposits.

It is to be expected that variations and modifications of this inventionwill readily occur to those skilled in the art upon reading the presentdescription. All such modifications are intended to be included withinthe scope of the invention as defined in the accompanying claims.

We claim:

1. A method of reducing the octane requirement of a dirty internalcombustion engine having lead-containing deposits on the surfacesforming the combustion chambers which comprises coating thedeposit-bearing combustion chamber surfaces with a compositionessentially comprising from about to 90% by weight of a viscous,metal-adhering vehicle that is non-corrosive to the engine parts andcontains from about 90 to 10% of an inorganic boron compound selectedfrom the group consisting of silver borate and copper borate, and thenrunning the engine.

2. The method defined in claim 1 in which the composition is coated onthe combustion chamber surfaces by introducing it through the spark plugopenings of the engine and the vehicle component of the composition is ahydrocarbon.

3. The method defined in claim 1 in which the vehicle component of thecomposition is a mixture of a petroleum bright stock having a viscosityof about 700 to 2300 SSU at 100 F. and a viscous synthetic polybutenehaving a molecular weight of about 700 to 1250.

4. A method of reducing the octane requirement of a dirty internalcombustion engine having lead-containing deposits on the surfacesforming the combustion chambers which comprises coating thedeposit-bearing combustion chamber surfaces with a compositionessentially comprising from about 50 parts by Weight of silver borate,55 parts by weight of a petroleum bright stock having a viscosity ofabout 1590 SSU at 100 F., and 25 parts by weight of a polybutene havinga molecular weight of about 840, and then running the engine.

5. A method of reducing the octane requirement of a dirty internalcombustion engine having lead-containing deposits on the surfacesforming the combustion chambers which comprises coating thedeposit-bearing combustion chamber surfaces with a compositionessentially comprising from about 60 parts by weight of copper borate,30 parts by weight of a petroleum bright stock having a viscosity ofabout 1590 SSU at 100 F., and 30 parts by weight of a polybutene havinga molecular weight of about 840, and than running the engine.

6. A composition for reducing the octane requirement of a dirty internalcombustion engine which comprises from about 10 to 90% by weight of aviscous, metaladhering essentially organic vehicle that is non-corrosiveto the engine parts and contains from about 90 to 10% of an inorganicboron compound selected from the group consisting of silver borate andcopper borate.

7. A composition for reducing the octane requirement of a dirty internalcombustion engine which comprises from about 10 to 90% by weight ofsilver borate and from about 90 to 10% by weight of a viscous,metaladhering, non-corrosive mixture of a petroleum bright stock havinga viscosity of about 700 to 2300 SSU at 100 F. and a polybutene having amolecular weight of about 700 to 1250.

8. A composition for reducing the octane requirement of a dirty internalcombustion engine which comprises from about 10 to 90% by weight ofcopper borate and from about 90 to 10% by weight of a viscous,metaladhering, non-corrosive mixture of a petroleum bright stock havinga viscosity of about 700 to 2300 SSU at 100 F. and a polybutene having amolecular weight of about 700 to 1250 9. A composition for reducing theoctane requirement of a dirty internal combustion engine which comprisesfrom about parts by weight of silver borate, parts by weight of apetroleum bright stock having a viscosity of about 1590 SSU at 100 F.,and 25 parts by Weight of a polybutene having a molecular weight ofabout 840.

10. A composition for reducing the octane requirement of a dirtyinternal combustion engine which comprises from about parts by weight ofcopper borate, 30 parts by Weight of a petroleum bright stock having aviscosity of about 1590 SSU at F., and 30 parts by Weight of apolybutene having a molecular Weight of about 840.

References Cited in the file of this patent UNITED STATES PATENTS1,848,831 Kodama Mar. 8, 1932 2,151,432 Lyons et a1 Mar. 21, 19392,552,555 Houdry May 15, 1951

1. A METHOD OF REDUCING THE OCTANE REQUIREMENT OF A DIRTY INTERNALCOMBUSTION ENGINE HAVING LEAD-CONTAINING DEPOSITS ON THE SURFACESFORMING THE COMBUSTION CHAMBERS WHICH COMPRISES COATING THEDEPOSIT-BEARING COMBUSTION CHAMBER SURFACES WITH A COMPOSITIONESSENTIALLY COMPRISING FROM ABOUT 10 TO 90% BY WEIGHT OF A VISXOUS,METAL-ADHERING VEHICLE THAT IS NON-CORROSIVE TO THE ENGINE PARTS ANDCONTAINS FROM ABOUT 90 TO 10% OF AN INORGANIC BORON COMPOUND SELECTEDFROM THE GROUP CONSISTING OF SILVER BORATE AND COPPER BORATE, AND THENRUNNING THE ENGINE.